1. Field of the Invention
The invention relates to a fingerprint apparatus, and more particularly to a semiconductor fingerprint apparatus with a flat touch surface.
2. Related Art
There are many known techniques of identifying an individual through the identification of the individual's fingerprint. The use of an ink pad and the direct transfer of ink by the thumb or finger from the ink pad to a recording card is the standard way of making this identification. Then, an optical scanner scans the recording card to get an image, which is then compared to fingerprint images in the computer database. However, the worst drawback of the above-mentioned method is that the fingerprint identification cannot be processed in real-time, and thus cannot satisfy the requirement of real-time authentication, such as network authentication, e-business, portable electronics products, personal ID card, security system, and the like.
The method for reading a fingerprint in real-time has become the important technology in the biometrics market. Conventionally, an optical fingerprint sensor may be used to read a fingerprint in real-time, as disclosed in U.S. Pat. Nos. 4,053,228 and 4,340,300. However, the optical fingerprint sensor has drawbacks because it is large in size and tends to be cheated by the fake image.
Consequently, silicon fingerprint sensors, which overcome the drawbacks of the optical sensor and are formed by silicon semiconductor technology, are developed. Based on the consideration of the manufacturing processes of the silicon integrated circuit, the capacitive or other electric field fingerprint sensor chip has become the most direct and simplest way.
FIG. 1 is a schematic illustration showing a conventional fingerprint apparatus 100. Referring to FIG. 1, the silicon semiconductor fingerprint apparatus 100 includes a package substrate 110, a fingerprint sensor 120, a plurality of interconnection wires 130 and an encapsulation layer 140. The fingerprint sensor 120 is disposed on the package substrate 110. The interconnection wires 130 electrically connect bonding pads 122 of the fingerprint sensor 120 to bonding pads 112 of the package substrate 110.
For application, the fingerprint apparatus has an exposed surface to be touched by the finger to sense the image of the finger textures. To achieve that, during the packaging process, a special mold and a flexible, soft material layer have to be adopted to protect the sensing surface of the fingerprint sensing chip, and two sides or the periphery of the packaged product are always higher than the middle sensing surface, as shown in FIG. 1.
According to the above-mentioned reasons, the conventional fingerprint apparatus has the high package cost and needs the special machine. In addition, because the external surface of the fingerprint sensing chip has to be exposed, the abilities of withstanding the electrostatic discharge and the force impact are deteriorated. Thus, the inconvenience of using the product is caused, and the lifetime of the product is shortened.
FIG. 2 is a schematic illustration showing the application of the fingerprint apparatus 100 of FIG. 1. As shown in FIG. 2, the fingerprint apparatus 100 is mounted on a notebook computer to serve as an apparatus for sensing the fingerprint and controlling the cursor to move on a screen by sensing the motion of the finger. Because the upper surface of the fingerprint sensor of FIG. 1 does not have an entirely flat touch surface, a special slide way 200 has to be formed on the notebook computer. Nevertheless, the swiping motions of the finger, especially the swiping motions along the left and right directions of FIG. 1, are still restricted by the projections on two sides. Thus, the user cannot control the mouse cursor at his or her will smoothly.
Therefore, it is an important subject to provide a semiconductor fingerprint apparatus with a flat touch surface but without the needs of the special mold and the conventional package.